Orthogonal gas laser device

ABSTRACT

One partial reflecting mirror ( 19 ) and two total reflecting mirrors ( 21  and  23 ) being placed at one end of a resonator ( 12 ) and three total reflecting mirrors ( 20, 22 , and  24 ) being placed at an opposite end of the resonator ( 12 ) are included, and the reflecting mirrors ( 19, 21 , and  23  and  20, 22 , and  24 ) are placed so that the centers of laser light on the three reflecting mirrors ( 19, 21 , and  23; 20, 22 , and  24 ) placed at each end of the resonator forms a triangle. Two ( 19  and  21; 20  and  22 ) of the three reflecting mirrors ( 19, 21 , and  23; 20, 22 , and  24 ) placed at each end of the resonator ( 12 ) are placed at a downstream end of a discharge area in a direction in which a laser medium ( 10 ) flows.

TECHNICAL FIELD

This invention relates to an improvement in an orthogonal-type gas laserand more particularly to an improvement in an orthogonal-type gas laserwhich contains a resonator consisting of a partial reflecting mirror anda plurality of total reflecting mirrors and turns laser light, therebymaking it possible to provide high output, save energy, and make thelaser compact.

BACKGROUND ART

FIG. 8 is a configuration drawing to show an orthogonal-type gas laserin a related art. In the figure, numeral 1 denotes a laser oscillator,numeral 2 denotes a discharge electrode in the laser oscillator 1,numeral 3 denotes a gas circulation blower in the laser oscillator 1,numeral 4 denotes a partial reflecting mirror, numeral 5 denotes a totalreflecting mirror, numeral 6 denotes a heat exchanger, numeral 7 denotesa cooling unit, numeral 8 denotes a power supply panel, numeral 9denotes a control unit, numeral 10 denotes a laser medium, and numeral11 denotes laser light taken out from the laser oscillator 1. Thepartial reflecting mirror 4 and the total reflecting mirror 5 make up aresonator 12. The cooling unit 7 cools the partial reflecting mirror 4,the total reflecting mirror 5, and the heat exchanger 6. A machine forgenerating discharge in the discharge electrode 2, a machine forcontrolling the gas circulation blower 3, a machine for producing avacuum in the laser oscillator 1, and the like are placed in the powersupply panel 8.

Next, the operation of the orthogonal-type gas laser in FIG. 8 will bediscussed. The machine for controlling the gas circulation blower 3 inthe power supply panel 8 is driven by a start signal from the controlunit 9, whereby the gas circulation blower 3 is rotated and the lasermedium 10 with which the laser oscillator 1 is filled, for example, CO₂gas in a carbon dioxide laser is circulated. In this state, if an outputsignal is given from the control unit 9, a high voltage is input to thedischarge electrode 2 and the laser medium 10 is excited because ofdischarge. The excited laser medium 10 emits light and drops to the baselevel. The emitted light is reflected and amplified between the partialreflecting mirror 4 and the total reflecting mirror 5 making up theresonator 12. That is, some of the laser light is taken out to theoutside from the partial reflecting mirror 4 and the remainder isfurther reflected on the total reflecting mirror 5 and is reflected andamplified repeatedly. The laser light 11 taken out to the outside iscontrolled so that the light corresponding to output of a command of thecontrol unit 9 is taken out. The configuration in FIG. 8 is calledthree-axis orthogonal type because the three directions of the directionof the laser light 11, the discharge direction, and the direction inwhich the laser medium 10 flows between the discharge electrodes 2 areorthogonal to each other. The laser light 11 taken out from the laseroscillator 1 is transmitted to a laser beam machine, etc., and is usedfor working of cutting, welding, etc., measuring, etc.

FIG. 9 is a configuration drawing to show the positional relationshipbetween reflecting mirrors and discharge electrodes in anorthogonal-type gas laser with a resonator configured for turning laserlight by three total reflecting mirrors, disclosed in Japanese PatentLaid-Open No. 127773/1985. FIG. 9(a) is a sectional view of viewinglaser oscillator from the optical axis direction of laser light 11. FIG.9(b) is a sectional view of viewing laser oscillator from a directionorthogonal to the optical axis direction of the laser light 11; it showsa laser light path. In the figure, numeral 12 denotes a resonator,numeral 13 is a partial reflecting mirror, numerals 14 to 16 denotetotal reflecting mirrors, numerals 17 denote apertures placed in frontof reflecting mirrors corresponding thereto and having a guide functionof shape determination of beam mode and laser light amplification, andnumeral 18 denotes a discharge space. The total reflecting mirrors 14and 15 are placed in the laser light path between the partial reflectingmirror 13 and the total reflecting mirror 16 and the laser lightreflected from the partial reflecting mirror 13 is turned three times bythe total reflecting mirrors 14, 15, and 16 and then is returned on thesame light path.

FIG. 10 is a drawing to show a gain distribution by discharge inorthogonal-type gas laser; it shows how the gain changes depending onthe position in the direction in which the laser medium 10 flows. FromFIG. 10, it is seen that the gain is higher downstream in the directionin which the laser medium 10 flows in the discharge area. Based on sucha characteristic, the laser light path is also placed at the downstreamend in the direction in which the laser medium 10 flows in theconfiguration in FIG. 9.

Next, the reason why the resonator 12 is configured for turning laserlight by a plurality of reflecting mirrors as in FIG. 9 will bediscussed based on theoretical expressions of lasing.

Laser output Wr is given by the following expression:Wr=η·(Wd−W 0)  (1)where η is excitation efficiency, Wd is discharge input, and W0 is alasing threshold value. The excitation efficiency η is given by thefollowing expression:η=F·η0  (2)where F is a discharge space utilization factor and η0 is conversionefficiency of laser medium to light.

The lasing threshold value W0 in expression (1) is given by thefollowing expression:W 0=w 0/m  (3)where w0 is a parameter derived from the loss of the whole resonatorsuch as the transmissivity of the partial reflecting mirror forming apart of the resonator and m is the number of times laser light isreturned.

From expression (1), it is seen that the higher the excitationefficiency η and the lower the lasing threshold value W0, the larger thelaser output Wr, namely, the higher the conversion efficiency to laserlight. From expressions (2) and (3), it is seen that the higher thedischarge space utilization factor F, the higher the excitationefficiency η and the larger the number of times laser light is returnedm, the lower the lasing threshold value W0 and therefore ahigh-efficiency orthogonal-type gas laser can be provided. Thus, theorthogonal-type gas laser with the resonator configured for turninglaser light by a plurality of reflecting mirrors is used for the purposeof providing a compact orthogonal-type gas laser having high conversionefficiency to laser light.

Such high efficiency provided by the configuration of turning laserlight by a plurality of reflecting mirrors is a characteristicphenomenon and cannot be realized until laser medium is excited bydischarge while laser light is reciprocated more than once in the samedischarge space. That is, it cannot be realized in the configuration inwhich only one optical axis exists in one laser tube like an axial-typegas laser, for example, disclosed in Japanese Utility Model Laid-OpenNo. 29969/1981.

The orthogonal-type gas laser has the configuration as shown above inFIG. 9 for enhancing the lasing efficiency of laser light; however,still higher efficiency is desired from the demand for energy saving inthis day and age. Demand for a more compact orthogonal-type gas laser isincreased from the viewpoint of saving space.

As the number of times laser light is turned is increased, efficiencycan be made higher as described above, but it is difficult to furtherincrease the number of times laser light is turned in the configurationin FIG. 9. The reason is that the spacing between the dischargeelectrodes is limited because of stable discharge generation andnormally is 100 mm or less and it is difficult to place all optical axesat the above-mentioned downstream end from the limitations on placementof the reflecting mirrors and the structure of a holder for holding thereflecting mirrors. Further, the reason is that the shape symmetry ofoutput laser light is degraded because of laser light overlap caused byturning laser light and directivity occurs in working using the outputlaser light, for example.

DISCLOSURE OF INVENTION

The invention is intended for solving the problems as described aboveand it is an object of the invention to provide an orthogonal-type gaslaser fitted for providing high output, saving energy, and being madecompact.

According to the invention, there is provided an orthogonal-type gaslaser comprising a laser oscillator containing a resonator consisting ofone partial reflecting mirror and a plurality of total reflectingmirrors, wherein at least five total reflecting mirrors are included.

An orthogonal-type gas laser comprises one partial reflecting mirror andtwo total reflecting mirrors being placed at one end of a resonator andthree total reflecting mirrors being placed at an opposite end of theresonator are included, and the reflecting mirrors are placed so thatthe centers of laser light on the three reflecting mirrors placed ateach end of the resonator forms a triangle.

Further, two of the three reflecting mirrors placed at each end of theresonator are placed at a downstream end of a discharge area in adirection in which a laser medium flows or in the proximity of thedownstream end.

Further, the partial reflecting mirror is placed at the downstream endor in the proximity of the downstream end.

Also, the partial reflecting mirror is placed upstream from thedownstream end and the diameter of laser light applied to the partialreflecting mirror is enlarged.

Further, the reflecting mirrors are placed so as to disperse the overlapdirections of laser light turn parts on the reflecting mirrors.

The invention, which is configured as described above, provides thefollowing advantages:

The orthogonal-type gas laser according to the invention is fitted forproviding high output, saving energy, and being made compact.

The thermal distortion of the partial reflecting mirror can besuppressed.

The shape symmetry of output laser light can be enhanced.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1(a) and 1(b) are configuration drawings to show a resonator partof an orthogonal-type gas laser according to an embodiment 1 of theinvention.

FIG. 2 is a drawing to show change in discharge space utilization factordepending on the number of times laser light is turned.

FIG. 3 is a drawing to show input/output characteristic.

FIGS. 4(a) and 4(b) are schematic representation to show the overlapstate of laser light turn parts and an example of output laser light.

FIGS. 5(a) through 5(d) are configuration drawings to show a resonatorpart of an orthogonal-type gas laser according to an embodiment 2 of theinvention.

FIG. 6 is a schematic representation to show a placement method ofreflecting mirrors to improve the shape symmetry of laser light whenapertures differ in diameter.

FIGS. 7(a) and 7(b) are configuration drawings to show anorthogonal-type gas laser according to an embodiment 3 of the invention.

FIG. 8 is a configuration drawing to show an orthogonal-type gas laserin a related art.

FIGS. 9(a) and 9(b) are configuration drawings to show the positionalrelationship between reflecting mirrors and discharge electrodes in anorthogonal-type gas laser in a related art.

FIG. 10 is a drawing to show a gain distribution by discharge inorthogonal-type gas laser.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a configuration drawing to show a resonator part of anorthogonal-type gas laser according to an embodiment 1 of the invention;FIG. 1(a) is a sectional view of viewing a laser oscillator from theoptical axis direction of laser light 11 and FIG. 1(b) is a schematicrepresentation to show a laser light path. In the figure, numeral 2denotes a discharge electrode, numeral 10 denotes a laser medium,numeral 11 denotes laser light, numeral 12 denotes a resonator, numeral18 denotes a discharge space, numeral 19 denotes a partial reflectingmirror, numerals 20 to 24 denote total reflecting mirrors, and numerals25 to 30 denote apertures.

Next, the operation will be discussed. The basic operation of theorthogonal-type gas laser is similar to that in FIG. 8 shown in therelated art. The laser medium 10 excited in the discharge space 18 isamplified in the resonator 12. In the resonator 12, laser light some ofwhich is reflected by the partial reflecting mirror 19 is turned and isreflected on the total reflecting mirrors 20, 21, 22, and 23 in orderstarting at the total reflecting mirror 20 and arrives at the totalreflecting mirror 24. The laser light reflected on the total reflectingmirror 24 is again reflected on the total reflecting mirrors 23, 22, 21,and 20 and arrives at the partial reflecting mirror 19 and some of thelaser light is taken out as the laser light 11. Thus, the totalreflecting mirrors 20 to 23 are placed in the laser light path betweenthe partial reflecting mirror 19 and the total reflecting mirror 24 andthe laser light reflected from the partial reflecting mirror 19 isturned five times by the total reflecting mirrors 20 to 24 and then isreturned on the same light path.

Next, an implementing method of such a turning configuration will bediscussed. It is desirable that the laser light path should be placed atthe downstream end in the direction in which the laser medium flows inthe discharge area from the gain distribution provided by dischargeshown in FIG. 10 in the related art. However, the spacing between thedischarge electrodes 2 is limited because of stable discharge generationand normally is 100 mm or less and it is difficult to place all opticalaxes at the above-mentioned downstream end from the limitations onplacement of the reflecting mirrors and the structure of a holder. Ifthe optical axes are placed at the above-mentioned downstream end at thetermination taking out the laser light, amplification of the laser lightreaches the maximum and thus good efficiency is provided. Therefore, asin FIG. 1(a), the optical axis between the apertures 25 and 26, theoptical axis between the apertures 27 and 28, and the optical axisbetween the apertures 26 and 27 are placed at the above-mentioned downstream end and other optical axes are placed upstream from theabove-mentioned down stream end, so that highly efficient and stablelasing can be provided.

FIG. 2 shows change in discharge space utilization factor depending onthe number of times laser light is turned; the configuration of theinvention in FIG. 1 corresponds to the case where the number of timeslaser light is turned is five and the configuration of the related artin FIG. 9 corresponds to the case where the number of times laser lightis turned is three. From FIG. 2, it is seen that the configuration ofthe invention provides a higher discharge space utilization factor thanthe configuration of the related art. It is also seen that the dischargespace utilization factor is not much raised if the number of times laserlight is turned exceeds five. Therefore, considering rise in theexcitation efficiency caused by improving the discharge spaceutilization factor, rise in costs caused by an increase in parts of thereflecting mirrors, etc., and the like, it is adequate that the numberof times laser light is turned is five. In an application to providehigher output, the number of times laser light is turned may be furtherincreased.

FIG. 3 is a drawing to show comparison between the configuration of theinvention in FIG. 1 and the configuration of the related art in FIG. 9with respect to the input/output characteristic under the same size andinput power conditions; the solid line indicates the configuration ofthe invention in FIG. 1 and the dashed line indicates the configurationof the related art in FIG. 9. In the configuration of the invention inFIG. 1, the out put efficiency is drastically enhanced because ofimprovement in the discharge space utilization factor and an increase inthe number of times laser light is returned, and the configuration ofthe invention in FIG. 1 can provide output about 1.4 times as high asthat of the configuration of the related art in FIG. 9.

Therefore, an orthogonal-type gas laser fitted for providing highoutput, saving energy, and being made compact can be provided.

Embodiment 2

If a resonator in an orthogonal-type gas laser is configured for turninglaser light by a plurality of total reflecting mirrors, an overlapoccurs in the laser light turn parts while the laser light is reflectedand amplified. Taking the configuration shown in FIG. 1 in theembodiment 1 as an example, in the laser light overlap part (forexample, the upper side of laser light coming from the aperture 25 andthe lower side of laser light going to the aperture 27 at the positionof the aperture 26 in FIG. 1), the upper side of laser light coming fromthe aperture 25 and the lower side of laser light going to the aperture27 scramble for the gain in the same space, and as for the portion, onlya gain of 50% each can be provided relative to the total gain 100%.Thus, the strength of the laser light overlap part drops to a halfrelative to the strength of a laser light non-overlap portion and theshape symmetry of laser light is degraded.

FIG. 4(a) shows overlap of laser light turn parts (A to D parts in FIG.1(b)), and the sum of the overlap portions for laser light becomesoutput laser light. FIG. 4(b) shows the output laser light in this case.Making a similar examination with FIG. 9 for the related art, overlapparts occur only at the top and the bottom of laser light and the shapesymmetry of output laser light is more degraded. If the shape symmetryof output laser light is degraded, directivity occurs in working usingthe output laser light, for example.

FIG. 5 is a configuration drawing to show a resonator part of anorthogonal-type gas laser according to an embodiment 2 of the invention;it shows the configuration for more improving the shape symmetry ofoutput laser light. Parts identical with or similar to those previouslydescribed with reference to FIG. 1 in the first embodiment are denotedby the same reference numerals in FIG. 5. FIG. 5(a) is a sectional viewof viewing a laser oscillator from the optical axis direction of laserlight 11 and FIG. 5(b) is a schematic representation to show a laserlight path. In placement of reflecting mirrors and apertures in FIG. 5,unlike that of the reflecting mirrors and the apertures in FIG. 1, areflecting mirror 22 and an aperture 28 and a reflecting mirror 24 andan aperture 30 are changed in position from those in FIG. 1. Therefore,the laser light path in FIG. 5(b) differs from that in FIG. 1(b)partially in overlap direction of laser light overlap parts. In thiscase, FIG. 5(c) corresponds to FIG. 4(a) and FIG. 5(d) corresponds toFIG. 4(b); the reflecting mirrors are placed and the laser light path isformed as in FIG. 5(a) and(b), whereby the overlap directions of thelaser light turn parts on the reflecting mirrors are dispersed as inFIG. 5(c) and the laser light overlap portions are dispersed and placedalmost on the perimeter of output laser light as in FIG. 5(d), so thatthe shape symmetry of the output laser light is improved.

In the configurations in FIGS. 1 and 5, the reflecting mirrors areplaced three each at both end parts of the resonator and the center oflaser light on the three reflecting mirrors at each end part of theresonator forms a triangle. This corresponds to placing the apertures25, 27, and 29 as a triangle and the apertures 26, 28, and 30 as atriangle in the example in FIG. 1 and corresponds to placing theapertures 25, 27, and 29 as a triangle and the apertures 26, 30, and 28as a triangle in the example in FIG. 5. Taking FIG. 5 as an example, ifthe apertures equal in diameter, the triangle formed by the apertures25, 27, and 29 is an isosceles triangle with the line connecting thecenters of the apertures 25 and 27 as a bottom, and the triangle formedby the apertures 26, 30, and 28 is an isosceles triangle with the lineconnecting the centers of the apertures 26 and 30 as a bottom. In theconfiguration in FIG. 5, when the apertures differ in diameter, if thecenter of the aperture 29 is placed at a position where a middle point Rof a line PQ connecting P and Q points, the points where the lineconnecting the centers of the apertures 25 and 27 crosses the outsideshapes of the apertures 25 and 27, is moved upstream in the direction inwhich a laser medium flows in parallel with discharge electrodes asshown in FIG. 6, the shape symmetry of the output laser light isimproved.

Embodiment 3

A partial reflecting mirror for taking out laser light involvesexcessive heat input and has a problem of occurrence of thermaldistortion, etc. To relieve such thermal distortion, a method ofenlarging the diameter of laser light applied to the partial reflectingmirror for decreasing the heat input amount per unit area is the mosteffective. In the placement of the reflecting mirrors and the aperturesin FIG. 1 in the embodiment 1 and in FIG. 5 in the embodiment 2, thetotal reflecting mirror 21 and the aperture 27 are placed above thepartial reflecting mirror 19 and the aperture 25 and thus it isdifficult to physically enlarge the diameter of laser light applied tothe partial reflecting mirror 19. Then, if the partial reflecting mirror19 and the aperture 25 are placed so that neither reflecting mirror noraperture comes above or below them as shown in FIG. 7, as compared withthe cases in FIGS. 1 and 5, the termination for taking out laser lightmoves to the upstream end from the downstream end in the direction inwhich the laser medium flows in the discharge area and thus output is alittle lowered, but it is made possible to enlarge the diameter of laserlight applied to the partial reflecting mirror 19 by changing theresonator as the curvature of the reflecting mirror is changed, etc.,changing the mode order, etc.

Therefore, the thermal distortion of the partial reflecting mirror canbe suppressed by adopting placement of reflecting mirrors and laserlight path as in FIG. 7.

Industrial Applicability

As described above, the orthogonal-type gas laser according to theinvention can provide high output, save energy and be made compact andthus production itself of the orthogonal-type gas laser is industriallyvaluable. Further, the orthogonal-type gas laser is fitted for use inindustries of working measuring, etc.

1. An orthogonal-type gas laser comprising: a laser oscillatorcontaining a resonator consisting of one partial reflecting mirror and aplurality of total reflecting mirrors, wherein one of said partialreflecting mirror and two of said plurality of total reflecting mirrorsare placed at one end of said resonator, three of said plurality oftotal reflecting mirrors are placed at an opposite end of saidresonator, and two of said three total reflecting mirrors placed at eachend of said resonator are placed at a downstream end of a discharge areain a direction in which a laser medium flows or in the proximity of thedownstream end and said partial reflecting mirror is placed upstreamfrom the downstream end and the diameter of laser light applied to thepartial reflecting mirror is enlarged so that centers of laser light onsaid three total reflecting mirrors placed at each end of said resonatorforms a triangle.
 2. The orthogonal-type gas laser as in claim 1,wherein said reflecting mirrors are placed so as to disperse overlapdirections of laser light turn parts on said reflecting mirrors.
 3. Anorthogonal-type gas laser comprising: a laser oscillator containing aresonator including one partial reflecting mirror and at least fivetotal reflecting mirrors, wherein said partial reflecting mirror and twoof said at least five total reflecting mirrors are placed at one end ofsaid resonator, three of said at least five total reflecting mirrors areplaced at an opposite end of said resonator, and said two of said atleast five total reflecting mirrors are placed at a downstream end of adischarge area in a direction in which a laser medium flows or in theproximity of the downstream end, and so that centers of laser lightcontinuously turned in the discharge area by said three total reflectingmirrors placed at each end of said resonator forms as triangle.
 4. Theorthogonal-type gas laser as in claim 3, wherein said reflecting mirrorsare placed so as to disperse overlap directions of laser light turnparts on said reflecting mirrors.
 5. The orthogonal-type gas laser as inclaim 3, wherein two of said three reflecting mirrors placed at each endof said resonator are placed at a downstream end of a discharge area ina direction in which a laser medium flows or in the proximity of thedown stream end.
 6. The orthogonal-type gas laser as in claim 5, whereinsaid reflecting mirrors are placed so as to disperse overlap directionsof laser light turn parts on said reflecting mirrors.
 7. Theorthogonal-type gas laser as in claim 5, wherein said partial reflectingmirror is placed at the downstream end or in the proximity of thedownstream end.
 8. The orthogonal-type gas laser as in claim 7, whereinsaid reflecting mirrors are placed so as to disperse overlap directionsof laser light turn parts on said reflecting mirrors.
 9. Theorthogonal-type gas laser as in claim 5, wherein said partial reflectingmirror is placed upstream from the downstream end and the diameter oflaser light applied to said partial reflecting mirror is enlarged. 10.The orthogonal-type gas laser as in claim 9, wherein said reflectingmirrors are placed so as to disperse overlap directions of laser lightturn parts on said reflecting mirrors.
 11. The orthogonal-type gas laseras in claim 1, wherein said triangle is an isosceles triangle.
 12. Theorthogonal-type gas laser as in claim 1, wherein the diameter of laserlight applied to said partial reflecting mirror is larger than thatapplied to at least one of said at least five total reflecting mirrors.13. The orthogonal-type gas laser as in claim 3, wherein said triangleis an isosceles triangle.